Spray head

ABSTRACT

A sprayhead for a pressurized aerosol dispenser includes an elongated expansion and mixing chamber upstream of the sprayforming nozzle orifice. Controlled expansion of the dispensed product and propellant mixture within the chamber enhances vaporization of the propellant, promotes uniform mixing of the vaporized propellant with the product prior to passage through the spray nozzle, and produces increased flow rates for a given nozzle orifice diameter.

United States Patent [191 i I [111 3,806,028

Coffey Apr. 23, 1974 [54] SPRAY HEAD 2,913,154 11/1959 Kuffer ..239/573UX 1,892,750 1/1933 Rotheim 239/573 X [751 Inventor! Charles Coll,Pmenas Park 2,697,635 12/1954, lvinset a1. 239/337 3,567,081 3/1971Meshberg ZZZ/402.17 [73] Assignee: Harris Paint Company, Tampa, Fla.

Primary Examiner--M.. Henson Wood, Jr. [22] F'led: 1972 AssistantExaminer-John J. Love [21] App1.No.:294,093" Attorney, Agent, orFirm--Kenyon & Kenyon Reilly Carr & Chapin Related US. Application Data[62] ggvisgczngsogfser. No. 120,169, March 2, 1971, Pat. [57] ABSTRACT Asprayhead for a pressurized aerosol dispenser in- 52 US. Cl. 239/1 dudesan elongated expansion and mixing Chamber 51 Int. Cl B05b 17/04 upstreamof the spray-forming nozzle orifice- [58] Field of Search 239/1, 1 1,468, 337, 573, trolled expansionof the dispensed product and P p 2 9579; 2 2 2 7 lant mixture within the chamber enhances vaporization ofthe propellant, promotes uniform mixing of the 5 References Citedvaporized propellant with the product prior to passage UNITED STATESPATENTS through the spray nozzle, and produces increased flow rates fora given nozzle orifice diameter. 2,621,014 12/1952 Efford 239/573 X3,669,359 6/1972 Focht. 239/579 3 Claims, 3 DrawingFigures 6 ZZ l SPRAYHEAD This invention relates to sprayheads for use with pressurizedaerosol dispensers for liquid products such as paint, and particularlyfor glitter paints having intermixed solid particles or flakes.

A conventional sprayhead of the pushbotton type generally has a centralpassageway in a stem leading from the outlet of a spring-loaded valvemounted in the top of an aerosol dispenser. The passageway connects witha cylindrical recess in the side wall of the pushbutton into which anozzle insert press fits, with the downstream face of the nozzle orificesubstantially flush with the exterior surface of the sprayhead. Thediameter of the sprayhead passageway and the inside diameter of thenozzle insert upstream of the orifice section are generally of the sameorder of magnitude, about onesixteenth inch. The throat diameter at theorifice may range from'0.0l6 inch to larger than 0.040 inch, dependingon the characteristics of the product dispensed. For relatively viscousliquids such as paint, a common orifice diameter is 0.032 inch, forexample.

In operation, axial movement of the sprayhead toward the valve causes itto open and allows a mixture of product and propellent to flow throughthe passageway and out the nozzle orifice in the form of an atomizedspray. The pressure and velocity of the outflowing stream aresubstantially constant from the valve outlet to the nozzle orifice,where the reduced throat diameter causes the velocity to sharplyincrease and the pressure to correspondingly decrease. Because the flowarea of the passageway from valve outlet to nozzle ori fice isrelatively small as well assubstantially uniform, propellantvaporization and product atomization apparently occur primarily in thereduced pressure region of the nozzle orifice, although some initialvaporization and mixing action does occur during flow through therelatively restricted valve port.

As a consequence of confining mixing and atomization to such a localizedregion adjacent the nozzle outlet, these conventionalsprayheads oftenproduce unsatisfactory spray patterns, particularly when used withliquid products having dispersed solid particles or flakes, such asspecialty paints containing flakesof metallic, plastic or glass glitter.The smallparticles this type of product apparently serve as nuclei foragglomerations of liquid in relatively large droplets that tendtospatter and collect inside the rim of the dispenser can and to producean uneven coating on the object being sprayed. These undesirable resultsintensify as the size of the suspended particles is increased.

Objects of the present invention are to eliminate the spattering problemwhen spraying liquids having intermixed solid particles, to increase theaverage particle size that can be sprayed with a nozzle orifice of givendiameter, and to increase flow rates for given dispenser pressures andnozzle orifice diameters.

These and other objects are obtained by incorporating an elongatedexpansion chamber upstream-of the nozzle orifice. Dimensions of theexpansion chamber are not critical; however, its diameter should besignificantly greater than that of the passageway leading from thevalve.

The chamber length should be preferably several times its diameter. Ithas been found that increasing the chamber length, for example, to atleast five times its diameter not only improves uniformity of the spraypattern but also, surprisingly, increases the product flow rate for agiven nozzle orifice diameter and propellant pressure.

In the drawings, FIG. 1 is a perspective view of an aerosol dispenserincorporating the sprayhead of the invention.

FIG. 2 is a section view of an embodiment of the invention.

FIG. 3 is a section perpendicular to the view of FIG. 1.

Referring to the figures, sprayhead 10 comprises an approximatelycylindrical body 12 having an axial passageway 14 with an inlet 16through a slot 18 at the end of a stem 20. The outside surface 22 ofstem 20 is sized to fit snugly in the outlet of a conventionalspringloaded valve 21 in the top of a pressurized aerosol dispenser 23.I

At its downstream end, passageway 14 opens through slot 24 intoexpansion chamber 26 in tube 28. Tube 28 is made of a deformable plasticmaterial, and its outside diameter is chosen to make an interference fitwith the bore 30 of cylindrical recess 32 in the side wall of sprayheadbody 12. Aconventional flanged nozzle insert 34 having an orifice 36 atits downstream face 38 force fits into the outer end of tube 28 to formthe downstream end of expansion chamber 26.

Although sprayhead body 12 and tube 2 8 are shown as a two-pieceassembly in the drawing, the assembly could be molded as a single piece,if desired. The important consideration is that the cross-sectional areaof expansion chamber 26 be significantly greater than thecross-sectional areas of both passageway 14 and orifice 36. Furthermore,the length of expansion chamber 26 should be several times its diameter;preferably the length-diameter ratio should be at least five. When thesprayhead is used with a typical domed-top aerosol dispenser of the typeshown in FIG. 1, the length of chamber 26 should also be preferably atleast enough to insure that the spray is delivered beyond the valvemounting cup 25.

In operation, sprayhead 10 is displaced axially by finger pressure onsurface 40, the spring-loaded valve 21 opens, and a mixture of liquidproduct and propellant flows through inlet 18, along passageway 14, andthrough slot 24 into expansion chamber 26. The abrupt increase in flowarea in expansion chamber 26 reduces the flow velocity, and the abruptchange in flow direction inducesa swirling flow that promotes intimatemixing of the product and the vaporizing propellant prior to dischargeas a fine spray through orifice 36.

Tests have been run to compare the performance of the above-describedsprayhead embodiment with an expansion chamber with that of aconventional sprayhead without an expansion chamber and also todetermine the effect of chamber length. Product used in the tests wasglitter" paint having intermixed solid particles with maximum dimensionsof about 0.008 inch.

Pertinent dimensions of sprayhead 10 were:

slot 18 l- 9323! u i J59-12iins 91 s Chamber 26 0.112 inch diameterOrifice 36 0.032 inch diameter For comparison, tests were run with twodifferent expansion chambers 26 having effective lengths of fiveeighthsand five-sixteenths inch, respectively. In addition, the sprayhead wastested without an expansion chamber but withnozzle insert 36 presseddirectly into recess 32.

By way of illustration, typical test results for the three sprayheadvariations described above used with 16- ounce capacity aerosoldispensers taken from a production line are listed below. Spray time ineach case was seconds.

Product Substantial variations from test to test preclude a quantitativecorrelation between chamber length and flow rate, but in every case theamount of product expended was greater with the long chamber than withthe short chamber and was greater with the short chamber than with nochamber.

As mentioned above, the size of inlet slot 18 in each of the three testsprayheads was 0.060 inch wide by 0.125 inch long. For comparison, asprayhead having no expansion chamber and an inlet slot size of 0.060inch wide by 0.055 inch long expended 21.3 grams in 5' seconds. It isthus clear that the size of inlet slot 18,

as would be expected, has a significant effect on flow rate. Withrespect to uniformity of spray pattern and absence from splatter,however, the incorporation of the expansion chamber of the presentinvention produced much greater improvement than did changes in size ofinlet slot l8.

In both tests with expansion chambers, the spray pattern was moreuniform and the glitter" particles more randomly distributed onthesprayed surface than in the test without an expansion chamber.Moreover, the flow rates as determined by container weighings before andafter equal duration spray bursts were greater in the tests with anexpansion chamber than those without, the difference being especiallymarked in the tests with the longer chamber. Greater flow rates, ofcourse, permit the operator to obtain desired coverage in a shortertime.

Other embodiments and dimensions will occur to those skilledin the art.For example, thelength of tube 28 could be extended to the edgeofcontainer 23 or even beyond, if desired. For liquids of differentviscosities and having different sized particles intermixed therein, thedimensions of slots 18 and 24 and the size of orifice 36 can be-variedaccordingly for optimum results.

Although the utility of the sprayhead of the present invention has beendescribed specifically in regard to spraying liquids having intermixedsolids, the invention is not limited to such application. Increased flowrates also result when spraying other fluids or fluid mixtures such asimmiscible liquids as well as liquids or solids in a gas. For example,the sprayhead produces superior results with enamels and works well.even when spraying cosmetic aerosol formulations such as talcum powder.In short, the sprayhead of this invention is applicable to all types offluids or dry mixes which are capable of being expended from apressurized aerosol dispenser.

What is claimed, is:

1. The method of spraying a mixture of pressurized aerosol propellantand a fluent material comprising the steps of:

flowing the mixture inward through an opening in a side wall of anupward-extending straight passageway near the lower end ofthepassageway. flowing the mixture upward through the passageway,

expanding abruptly the flowing mixture through an opening in the' sidewall of the passageway near the upper end of the passageway into anelongated expansion chamber having a length at least five times itsdiameter and a cross section substantially larger than that of theopening into the expansion chamber and that of the upward-extendingpassageway,

the expansion chamber extending laterally in a direction-transverse tothe upwardextending passageway whereby a swirling motion is imparted tothe comprises dry solid particles.

1. The method of spraying a mixture of pressurized aerosol propellantand a fluent material comprising the steps of: flowing the mixtureinward through an opening in a side wall of an upward-extending straightpassageway near the lower end of the passageway. flowing the mixtureupward through the passageway, expanding abruptly the flowing mixturethrough an opening in the side wall of the passageway near the upper endof the passageway into an elongated expansion chamber having a length atleast five times its diameter and a cross section substantially largerthan that of the opening into the expansion chamber and that of theupward-extending passageway, the expansion chamber extending laterallyin a direction transverse to the upwardextending passageway whereby aswirling motion is imparted to the flowing mixture upon changingdirection as it enters the expansion chamber, and then accelerating theexpanded flowing mixture directly from the expansion chamber through aconstricted nozzle orifice coaxial with the expansiOn chamber and havinga cross-sectional area smaller than that of the opening into theexpansion chamber, whereby the mixture issues from the orifice in theform of a finely divided, well mixed spray.
 2. The method of claim 1wherein the fluent material comprises a liquid having solid particlesinterspersed therein.
 3. The method of claim 1 wherein the fluentmaterial comprises dry solid particles.